I've always liked this video.

With my original truck, I really had to 'learn' the limitations of "four wheel drive". I can hardly wait to test out my runner over the same terrain and put atrac to the test this summer.

http://www.richmondgear.com/PTRAX2.wmv



J

Thats an interesting video.....

Based on the limited-slip in that video, ATRAC is much closer to the locker than the limited-slip.

When you go to play around, one thing you might try is to find a nice, steep dirt hill and mess around in low range with the center diff locked. If you apply the gas just right, ATRAC is very close to a locker. The tires will spin more with too much gas. I still have to get my mind right before steep hills. If I don't concentrate, I react to wheel slippage with too much pedal.

That limited slip looked like it needed of a few more clutch packs.

I haven't tried the atrac myself yet in the snow and ice. I will be suprised and very impressed it the atrac and open differentials on the 4runner will be as predictable and good on snow and ice as and my old ford 8.8s with a bunch of clutch packs. The pics I have seen look promising.

How predictable is the atrac at speeds over 40 in the snow?Is it delayed? With the limited slips I had in my last suv it had amazing predictable traction in the snow. It simply went where ever you pointed it with no delay. As a side note I drove a different 00 explorer in the same conditions with the 4.0l v6 and fords auto 4x4. It has terrible lag for the 4x4 to kick in when in auto mode and the rear wheels started slipping. The lag and sudden jerk of when it kicked back in caused it to be a lot more unstable at driving on roads at fast speeds with changing conditions. Of course this other explorer had open differentials as well.

I had a '97 with no locker and hit a few trails and the open diffs do show up on steep rockey hills but with my '99 w/locker it's like night and day. Just did Slaughterhouse Gulch outside of Denver and the trail wasn't too hard but it is a nice challenge for a mostly stock 4Runner.

http://www.traildamage.com/trails/index.php?id=2

That video is pure BS.

The old Ford truck at the end had enough forward momentum to roll through the ramp in neutral!

If they really wanted to make a point, they would have stopped the truck in the middle of the ramp and then pulled the boat over it.

Pathetic attempt, if you ask me.

How about a vid with actual off roading diff of the locked and unlocked. I've seen a few 3rd gens struggle with hills and open diffs and seeing and driving a locked Runner would make a good comparison to show what a locker really does.

I was also concerned the the locked ford had to much momentum. Technically, they should have brought it to a complete stop for full effect.

Check that site for a few other videos, some show 'locked' v. unlocked going up and down a hill.

Still, it proves the point that the big Ford and Dodge 'limited slips' are not "all that.

I recall once we were swimming at a lake. A ford f-150 backed in pretty deep to release a boat. It was a model with ltd slip. In 2wd it could not exit the water. He put it in 4 and crawled out. We were confident that with my brother in laws lockable diff (chevy) he could have done the same thing in 2wd. (note: I love ford, but this is what I observed)

J

The good thing about limited slips are they are cheap to rebuild. Get some cluth pack, shims, thrust washer and bearing and you are good to go. If you want your limited slip so lock up sooner and hold tighter all you have to do is pack it tighter with some extra clutch packs. Very easy and cheap to do.

I loved having front and rear limited slips in my last suv and found them to be very predictable in bad weather especially at speed when having to make an unexpected manuever.

I hope that the 4runner's atrac is not delayed or slow when doing it's thing at road speed. I have no doubt that it will be able to distribute some torque through it's open differentials by applying the brakes. The same theory has been a trick used by off-roaders for a long time except they just had do do it manually. It does work at transfering the torque to the other axle by creating resistance on the side that is spinning.

My understanding is that some have dissabled atrac by unplugging a plug near the master cylinder. To me this seems like a disadvantage because you then have a 4x4 with open differential and no convieniant way to limit torque from only going to one axle. I have also heard people mention that the vehicle felt sluggish which could suggest the vehicle is put into a "Limp" mode by unplugging the conector which will decreace it's performance.

I haven't had the oppourtunity to try out atrac myself yet but I will in the future. In the mean time I am relying everyone's elses experiance and what they have owned to compare it to in the mean time.

I hope it works as well as a traditional limited slip and proves reliable down to the expensive electronics and parts that control it.
I guess it is a new age where fixing you limited slip system means replacing some expesive computer or an expensive calliper or speed sensor compared to throwing a few clutch packs in for $30-60 in parts at most to repair a differential to keep it functioning as a limited slip. That is one concern I have with the Atrac system in the long run compared to an old school limited slip.

A few things to remember:

- Video is cool. But that last part with the old Ford truck with PowerTrax is bogus...as stated above, too much momentum. Cool video nonetheless because it shows the difference between open diff vs. factory LSD (the video's only true value).

- Factory LSD's are not all equal. Some are better than others.

- ATRAC would have done the above exercise easily. However, if the 4runner was pulling a heavy boat, then i am not sure if ATRAC can send enough torque to the tire(s) with traction to pull across the platform. ATRAC can only send so much torque...the rest is dissipated in heat from the braking action of the spinning wheel.

- ATRAC is NOT meant to work at high speed.

- From my readings of most ATRAC systems (Mercedes & Land Rover), they stop working past 38-40 mph. I doubt that Toyota system is any different. ATRAC is for low speed traction only. Keep your RPM below 3-3.5K and ATRAC will work well.

- At high speeds (> 40 mph), the thing that will save your butt is NOT ATRAC, but stability control (VSC). Thus, i would feel perfectly safe in a 4runner above 40 mph...i would trust it way more than any older 4x4 without VSC.

Hope this helps.

Yes that does help. That is something I did not know about it.

. Let me ask you this.... How many mercedes and land rover's that were built to 4x4.... used atrac, and did not have a locking differential option also to lock up at least the rear if you needed it for a true split side to side?

And yes all factory limited slips are not created equal. I have seen some already doing the one wheel burnout before the vehicle left the lot.

Please read the summary below if you're in a hurry.

Mercedes started using ATRAC in their SUV in 1998 with the M-class introduction. Land Rover started a bit earlier i think with the previous generation of Range Rover...however, i am not too sure on this. For sure, the 2001 Discovery Series II had ATRAC and 2003 RR had it too.

Mercedes did not have any locker option...only in 2006 does the M-class have an off-road package with rear locker (not available in USA). The new 2007 Mercedes GL-class does have a rear locker as option (available in USA). Both today's M-class and GL-class use ATRAC.

Land Rover did not introduce a rear locker until the introduction of LR3. Before that, it was open diff with ATRAC (Discovery Series II). The Discovery Series I was open diff with no ATRAC. That was why Land Rover depended so much on wheel articulation to get over obstacles. The Discovery S1 did have a center diff lock that was not available in Series II until 2004. The current Range Rover does not have a locking center diff nor a rear locker...only Torsen center diff (non-lockable) and ATRAC.

Summary: (remember, this is based on MY MEMORY...so check these before committing to it. I am on a break from gardening.)

Mercedes:
1979-1998 = Mercedes only SUV is G-wagen (not officially sold here)...front, center, rear lockers; no ATRAC
1998 = Mercedes M-class with ATRAC
2002 = Mercedes G500 official USA introduction with ATRAC & full set of lockers
2006 = Mercedes M-class 2nd generation with ATRAC and optional rear locker (in other parts of the world)
2007 = Mercedes GL-class with ATRAC and rear locker as option

Land Rover:
Before 2001 = Land Rover Discovery SI had open diffs and no lockers
2001 = Land Rover Discovery SII introduction with ATRAC (no center diff lock)
2003 = Range Rover MKIII was introduced with ATRAC, cross-linking air suspension, and Torsen center diff (not manually lockable however)
2004 = Land Rover Discovery SII with center diff lockable
2005 = Land Rover LR3 introduction with Terrain Response which totally incorporates ATRAC, center diff lock, and optional rear locker
2006-7 = Range Rover is supposed to also have Terrain Response....

Hope this helps.

Yes. That helps a ton....

I'm not too sure about that. I was traveling at ? (Well, at a fast clip) when I hit a deep puddle with the left front wheel and hydroplaned, I could swear the ATRAC kicked in and out instantly. I was traveling on a straight highway and the right side wheels were on dry ground. I was very impressed with how quickly it reacted and how the vehicle didn't skip a beat. When I experimented with the VSC it did not act that way and it was not as quick to react and return to normal driving.

Koz

I too had mine kick in at about 55 when I accidently got slightly airborn going over some railroad tracks. Beep beep beep beep.....
or was it vsc?


I'm betting disabling the traction control can be done electrically in one of the ecu's.
Ford systems are under module programming/ customer preference items and a tech can enable / disable traction control.....